Is it even Psyonix's fault? You either get Screen tearing or you get input lag unless you have gsync/freesync and it's always been like that on PC and every other PC game ever unless you have a monitor/tv with a higher refresh rate. I don't see an issue here seeing as technology is the limiting factor unless I am missing something.

Vsync does cause more latency because it delays frames from being shown on the screen due to syncing up the monitor and GPU frames. That makes it so that the time from when you do something to when it's shown on the screen longer. It's not necessarily affecting the controllers, it's just affecting when you see it. Lot's of things affect input lag, including the display (game mode on a TV tries to limit the lag, although a gaming monitor is going to give you the best performance over a TV display).

I'm not sure about the cause of the tearing, could be this particular game, but could also be the fact that now that it's running 4K, the GPU is causing the frame rate to drop suddenly due to the increased demand from the GPU in higher resolutions. The frame drops are significant enough to cause the tearing, which is just what you get when the display and source are not synced. You don't notice the tearing at higher frame rates when you are playing on lower resolution like 1080p but they are still there at some level.

It's the reason why on 4K gaming on PC's technologies like AMD Freesync and Nvidia Gsync are so important, the reduce the tearing but don't cause as much input lag as vsync. I should probably just google this but does Xbox support Freesync? Might be worth looking for a display that supports that technology if so.

Vsync has to do with locking the frames of the game to the framerates sets in Rocket league on xbox it is (Supposedly) 60. Will eliminate screen tearing, but because it has to wait for a new frame to refresh the screen every 1/60th of a second, it does add a lot of input lag.

Hard to explain, but just basically vsync on for looks, vsync off for performance

Isn't the point of the game now running 4K60 that it's outputting a constant 60fps, and thus v-sync should not be necessary? Unless it's not really outputting 60FPS. I which case I'll gladly take a res cut for that ...